The "Rocks"

Developing "non-obvious" containers in which we can hide our instrumentation is one of the early goals of the project.  Through the design and construction efforts of Michael Lurvey (assisted by Monica Meiji and Ted), we are now producing containers that appear to be rocks.

The two pictures below show the "alpha" rock from the top and the bottom.
Real rocks are used as models for a latex casting.  This is created from several layers that are applied with a brush, followed by a gauze wrapping, and finally several more layers of latex.  

Before the latex mold is removed, a plaster of Paris mold is built around the outside.  After this is dry, it is split and removed.  The latex mold can be peeled off at this time.

The plaster of Paris mold holds the more flexible latex mold during the next casting stage.  "Bondo" is used to recreate the rock as a shell.  This takes the application of several layers.
Once the casting has been made, the bottom is flattened.

A Plexiglas bottom cover is cut following the shape of the bottom of the rock.  The interface board is attached to the inside of this bottom cover.  

Holes are drilled through the Plexiglas, into the rock.  Self tapping screws are used to attach the bottom to the rock.  A gasket of small surgical tubing is used as a seal.  The wire exit is sealed with silicon compound.
Once the wires are attached and the rocks are sealed, they are ready for final checking before deployment.  Here, several rocks await checking in the lab.

The rain gauges need to be calibrated at this stage.  That involves running them with a known amount of water and leveling them so that each side of the tipping bucket gets an equal number of counts.

A basic deployment unit consists of a rock, a recording rain gauge and a re-purposed computer.

Last Updated: 09/20/00